19. Letters of Transit

Complete story — includes the ending

In 2036, the Observers have taken over the Earth and established a totalitarian regime using their superior technology and their ability to read the minds of most humans. They are helped by human "Loyalists". Some members of the current Fringe team, including Etta and Simon, are part of the resistance. Walter has spent the past 21 years in amber and has recently been freed in the hope that he will be able to build a device that will allow humankind to defeat the Observers. However, his brain has been damaged and he does not remember how to build the device. Simon and Etta turn to Nina, learning that Walter had William Bell remove a piece of his brain. The team manage to retrieve it from the old Massive Dynamic facility, tightly controlled by Observers, in part due to the inability of the Observers to read Etta's mind, and restore Walter's memories. Walter explains that the Observers made the Earth uninhabitable by 2609, traveled back in time and took over the planet. He kills approaching Observers and Loyalists using an antimatter bomb, then he leads Simon and Etta to where Peter, Astrid and William Bell have been ambered. Astrid is freed. Simon sacrifices himself to the amber in order to push Peter free, while Walter severs Bell's hand for later use. Peter realizes that Etta is his daughter.